The Printed Book

by Harry G. Aldis, M.A. Cambridge at the University Press 1916

Construction of a Book Part 2

For a folio book this method will not serve; since, for the sake of convenience in binding, two or more sheets are inserted into each other, like a section of ordinary note-paper. In this case, as also in the case of many early printed books which have no printed signatures, assistance can be obtained from the watermark, that is, the semi-transparent device found in almost every sheet of all except modern paper. By holding a leaf up to the light the position of the watermark can be observed. If it occurs in the middle of the page the book is a folio, and in this case it will be noticed that the chain lines (the semi-transparent lines an inch or more apart) in the paper run vertically through the leaf. If the watermark is in the middle of the inner margin and cut in half by the fold at the back of the book, with the chain lines horizontal, the book is a quarto. In an octavo the watermark will be found at the top of the inner margin of the page, with the chainnes vertical as in a folio. The determination of smaller sizes- 12mo, 16mo, 24mo-is more complicated, and explanation may be sought in the more elaborate bibliographical treatises.

How it happens that the watermark occurs in these positions can be easily demonstrated by marking a circle in the middle of the first page of a sheet of note-paper and observing where the circle comes when the sheet is folded. This folded sheet will also shew why it is that, in books which have not had their edges cut in the process of binding, the top and some of the front edges have to be cut with a paper-knife before the book can be used. If there are neither signatures nor watermarks visible, as happens in some early books, there is yet one other clue.

Open the book and turn over the leaves until an opening is found where the thread of the sewing shews along the back between the two pages. This opening will be the middle of a sheet, and the number of leaves between this and the middle of the next opening where the thread shews !n like manner, will be the number of leaves in a sheet. To many modern books none of these methods will apply. For, since large printing machines came into use, a greater number of pages can be printed at one operation than in the days of the old hand-press; and paper is now made in almost any size to suit the convenience of the printer. Moreover, neither watermark nor chain lines are to be seen in most modern machine-made paper.